The general aim of this program is to study the regulation of the cardiovascular system in the unanesthetized primate. Because anesthetics change the activity of the nervous system, and possibly, even the responsiveness of the cardiovascular system at the tissue level, techniques have been devised to assess cardiovascular responses in trained, awake monkeys. Manipulations of the nervous system or introduction of drugs are used to assess the function of the cardiovascular system. With these techniques it has been possible to simulate stress situations which force the cardiovascular system to extreme levels of activity, thereby making possible the study of the nervous system influences on cardiovascular responses during periods of emotion and exercises. These studies then become a model of human stress situations and will shed direct light on the neural mechanisms leading to pathological conditions such as essential hypertension and other cardiovascular pathology. At the same time and of equal importance, these studies also are designed to investigate the neural mechanisms underlying the psychological experience of emotion. Heretofore information has been available that the hypothalamus and parts of the brain stem do influence cardiovascular function and various hypotheses have been put forward as to what role these areas may play in control. However, direct tests of these ideas through the mechanisms of behavioral control techniques have rarely been successfully realized.